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BUFFALO, N.Y. -- Modern glaciers, such as those making up the
Greenland and Antarctic ice sheets, are capable of undergoing
periods of rapid shrinkage or retreat, according to new findings by
paleoclimatologists at the University at Buffalo.

The paper, published on June 21 in Nature Geoscience, describes
fieldwork demonstrating that a prehistoric glacier in the Canadian
Arctic rapidly retreated in just a few hundred years.

The proof of such rapid retreat of ice sheets provides one of
the few explicit confirmations that this phenomenon occurs.

Should the same conditions recur today, which the UB scientists
say is very possible, they would result in sharply rising global
sea levels, which would threaten coastal populations.

"A lot of glaciers in Antarctica and Greenland are
characteristic of the one we studied in the Canadian Arctic," said
Jason Briner, Ph.D., assistant professor of geology in the UB
College of Arts and Sciences and lead author on the paper. "Based
on our findings, they, too, could retreat in a geologic
instant."

The new findings will allow scientists to more accurately
predict how global warming will affect ice sheets and the potential
for rising sea levels in the future, by developing more robust
climate and ice sheet models.

Briner said the findings are especially relevant to the
Jakobshavn Isbrae, Greenland's largest and fastest moving tidewater
glacier, which is retreating under conditions similar to those he
studied in the Canadian Arctic.

Acting like glacial conveyor belts, tidewater glaciers are the
primary mechanism for draining ice sheet interiors by delivering
icebergs to the ocean.

"These 'iceberg factories' exhibit rapid fluctuations in speed
and position, but predicting how quickly they will retreat as a
result of global warming is very challenging," said Briner.

That uncertainty prompted the UB team to study the rates of
retreat of a prehistoric tidewater glacier, of similar size and
geometry to contemporary ones, as way to get a longer-term view of
how fast these glaciers can literally disappear.

The researchers used a special dating tool at UB to study rock
samples they extracted from a large fjord that drained the ice
sheet that covered the North American Arctic during the past Ice
Age.

The samples provided the researchers with climate data over a
period from 20,000 years ago to about 5,000 years ago, a period
when significant warming occurred.

"Even though the ice sheet retreat was ongoing throughout that
whole period, the lion's share of the retreat occurred in a
geologic instant -- probably within as little as a few hundred
years," said Briner.

The UB research reveals that the period of rapid retreat was
triggered once the glacier entered deep ocean waters, nearly a
kilometer deep, Briner said.

"The deeper water makes the glacier more buoyant," he
explained.

"Because the rates of retreat were so much higher in the deep
fjord, versus earlier when it terminated in more shallow waters or
on land, the findings suggest that contemporary tidewater glaciers
in Greenland and Antarctica that are retreating into deep waters
may begin to experience even faster rates of retreat than are
currently being observed," said Briner.

Right now, Jakobshavn Isbrae is draining into waters that are
nearly a kilometer deep, he said, which means that its current
rates of retreat -- as fast as 10 kilometers in the past decade --
could continue for the next hundred years.

"If modern glaciers do this for several decades, this would
rapidly raise global sea level, intercepting coastal populations
and requiring vast re-engineering of levees and other mitigation
systems," said Briner.

Co-authors on the paper were Aaron C. Bini, formerly a master's
of science candidate in the UB Department of Geology, and Robert S.
Anderson, Ph.D., in the Department of Geological Sciences at the
University of Colorado, Boulder.

Briner's research was funded by the National Science
Foundation.

The University at Buffalo is a premier research-intensive public
university, a flagship institution in the State University of New
York system and its largest and most comprehensive campus. UB's
more than 28,000 students pursue their academic interests through
more than 300 undergraduate, graduate and professional degree
programs. Founded in 1846, the University at Buffalo is a member of
the Association of American Universities.